High Efficiency Power Production Methods, Assemblies, and Systems

ABSTRACT

The present disclosure provides methods, assemblies, and systems for power production that can allow for increased efficiency and lower cost components arising from the control, reduction, or elimination of turbine blade mechanical erosion by particulates or chemical erosion by gases in a combustion product flow. The methods, assemblies, and systems can include the use of turbine blades that operate with a blade velocity that is significantly reduced in relation to conventional turbines used in typical power production systems. The methods and systems also can make use of a recycled circulating fluid for transpiration protection of the turbine and/or other components. Further, recycled circulating fluid may be employed to provide cleaning materials to the turbine.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/385,039, which was filed on Sep. 21, 2010, U.S.Provisional Patent Application No. 61/385,047, which was filed on Sep.21, 2010, and U.S. Provisional Patent Application No. 61/437,330, whichwas filed on Jan. 28, 2011. The disclosures of the referencedapplications are hereby incorporated herein in their entirety byreference.

FIELD OF THE ENDEAVOR

The present disclosure provides turbine and combustor components thatmay be used in power production methods and systems. The disclosure alsoprovides methods of using such turbine and combustor components in powerproduction.

BACKGROUND

Gas turbines are routinely used in power production systems and methodsto extract energy from a flow of combustion gases that is directedacross blades present in the turbine to spin a turbine shaft. Energy maybe extracted from the rotating shaft by an electrical generator toprovide power in the form of electricity. Due to the extreme conditions(e.g., high temperatures and presence of erosive and/or corrosivematerials) under which gas turbines are operated in typical powerproduction plants (e.g., coal burning power plants), gas turbinecomponents are typically formed of high performance materials. Thus, gasturbines often are high cost components of power production facilities.

Existing turbines may operate with inlet temperatures from about 1200°C. to about 1400° C. with blade temperatures from about 900° C. to about1000° C. Thus, gas turbines operating in power production facilitiestypically require the use of superalloy materials to withstand the hightemperatures. Moreover, for most advanced applications, blade coolingalso is required along with the use of advanced fabrication technology,such as directionally solidified materials and even single crystal bladetechnology. Blade cooling is used to help improve turbine temperaturetolerance, and thus efficiency, but this process has been limited by thefact that only air, or in some cases steam, has been available forcooling. The quantity of air available for cooling is limited by theamount of energy available to compress and pump the air and sometimessteam through the turbine blades. Moreover, the air typically isprovided at a limited pressure—e.g., close to atmospheric pressure—andthus has limited heat transfer capabilities, even at high flow rates.Further, air contains large amounts of oxygen, which is highly reactiveat high temperatures, and this is another factor that tends to requirethat turbine blade metallurgy be restricted to highly oxidationresistant materials, such as superalloys. Thus, despite the use ofadvanced materials and cooling, gas turbine blades still are plagued byoxidative and in some cases steam degradation.

While fossil fuel sources are being depleted, there remain vast reservesof coal that could be used in power production, but combustion of suchsolid fuels results not only in pollution but also particulates that cancause damage to components of power production systems, particularlyturbine blades. Such damage particularly arises from particles incombustion product flows impacting turbine blades at highvelocities—e.g., up to and exceeding 600 mph (268 m/s). Previousattempts to mitigate such damage have included the requirement forfiltration systems to remove particulates from combustion product flowsprior to passage through the turbine, as well as the use of highperformance materials in blade construction, as noted above. Suchrequirements, however, increase the cost of power production systems.Moreover, such requirements increase the complexity of power productionsystems and can reduce efficiency of the power production methods.Accordingly, there is a need for improved gas turbine blade technologythat overcomes at least the foregoing limitations in the art.

SUMMARY OF THE DISCLOSURE

The present disclosure provides methods, assemblies, and systems forpower production that can allow for increased efficiency and lower costcomponents arising from the control, reduction, or elimination ofturbine blade chemical degradation by air and steam and by mechanicalerosion by particulates in a combustion product flow. The methods,assemblies, and systems can comprise the use of higher pressure fluidflows and/or turbine blades with increased total blade area that allowfor a required power generation with a substantial reduction in bladevelocity and in blade temperature. The disclosure particularly providesfor turbines that are significantly smaller in at least one dimensionand with cooler blades in comparison to turbines used in conventionalpower production systems. Such turbines particularly can be incorporatedinto a power production method or system. For example, the method orsystem can be one that incorporates the use of a high pressure, highrecycle ratio circulating or working fluid, such as a CO₂ circulatingfluid. Moreover, blade cooling technology can be combined with the bladedesign, operation pressure, and operation velocity to allow forcustomization of turbine operation within a range of temperatures,pressures, and speeds that control, reduce, or eliminate erosion arisingfrom particle impingement or chemical degradation of the turbine blades.Particularly, the turbine blades can incorporate transpirationprotection via passage of a transpiration fluid (e.g., the recycledworking fluid) through the turbine blades. Such transpiration protectioncan include blade cooling, depending upon the temperature of thetranspiration fluid used. Since the turbine blades can rotate at asignificantly reduced velocity in relation to turbine blades inconventional power production systems, the disclosure may provide forreduction in erosion, increased blade lifetime, and reduction in bladestrength requirements. Moreover, the inventive turbines may operate athigher efficiency and lower temperatures, which enables lower operatingcosts, longer in-service time, and lower fuel use.

In one particular embodiment, a method of power generation is provided.The method may comprise introducing a fuel, O₂, and a circulating fluidinto a combustor, combusting the fuel in the combustor to provide acombustion product stream including the circulating fluid and a contentof particulates, the combustion product stream flowing at a definedvelocity, and expanding the combustion product stream across a turbinecomprising a plurality of turbine blades to generate power and output aturbine discharge stream, the turbine being operated such that theturbine blades rotate at a blade velocity of less than about 500 mph.

The method may further comprise passing the turbine discharge streamthrough a filter configured to remove substantially all of theparticulates contained in the turbine discharge stream and form afiltered turbine discharge stream. The method may also comprise passingthe filtered turbine discharge stream through a heat exchanger toprovide a cooled turbine discharge stream, treating the cooled turbinedischarge stream to withdraw one or more components of the turbinedischarge stream, and passing the treated turbine discharge stream backthrough the heat exchanger to provide a heated, recycled circulatingfluid stream. The method may additionally comprise directing at least aportion of the heated, recycled circulating fluid stream to thecombustor. Further, the method may comprise directing at least a portionof the heated, recycled circulating fluid stream to the turbine. Also,the method may comprise directing at least a portion of the heated,recycled circulating fluid stream to a cleaning material unit whereinthe heated, recycled circulating fluid stream is combined with acleaning material to form a cleaning material stream, the cleaningmaterial in the cleaning material stream being configured to removedeposits on the turbine blades arising from the content of particulatespresent in the combustion product stream.

The cleaning material stream may be input directly into the turbine.Further, the cleaning material stream may be combined with thecombustion product stream to form a combined combustion product andcleaning material stream that may be directed into the turbine. Thecirculating fluid may comprise CO₂, which may be provided in asupercritical state. Additionally, the method may include combining thefiltered turbine discharge stream with a particulate sold fuel to forman additional fuel in the form of a slurry, and introducing theadditional fuel to the combustor. Also, the method may include using atleast a portion of the circulating fluid that is recycled as atranspiration fluid. Using the circulating fluid that is recycled as thetranspiration fluid may comprise transpiring the transpiration fluid toan exterior surface of the turbine blades. Transpiring the transpirationfluid to the exterior surface of the turbine blades may comprisetranspiring the transpiration fluid through a porous sintered material.

In another embodiment a power generation system is provided. The powergeneration system may comprise a combustor configured for receiving afuel, O₂, and a circulating fluid, and having at least one combustionstage that combusts the fuel and provides a combustion product streamincluding the circulating fluid and a content of particulates, a turbinein fluid communication with the combustor, the turbine having an inletfor receiving the combustion product stream, an outlet for release of aturbine discharge stream, and a plurality of turbine blades ofsufficient dimensions such that the turbine operates at a blade velocityof less than about 500 mph, and a filter in fluid communication with theoutlet of the turbine and configured to produce a filtered turbinedischarge stream.

The power generation system may further comprise a heat exchanger influid communication with the filter and configured to receive thefiltered turbine discharge stream. The power generation system may alsocomprise a cleaning material unit in fluid communication with the heatexchanger, the cleaning material unit being configured to combine acleaning material with a fluid stream received from the heat exchangerto form a cleaning material stream. The power generation system mayadditionally include a flow combiner switch configured to combine thecleaning material stream with the combustion product stream to form acombined combustion product and cleaning material stream and direct thecombined combustion product and cleaning material stream to the turbine.

The blades may comprise a porous sintered material, and the poroussintered material may be configured to direct a transpiration fluid toan exterior surface of the blades. The porous sintered material maydefine the entirety of the exterior surface of the blades. Further, theturbine may comprise a rotor, and the rotor may comprise the poroussintered material and the porous sintered material may be configured todirect the transpiration fluid to an exterior surface of the rotor.

In another embodiment a method of power generation is provided. Themethod may comprise introducing a fuel, O₂, and a CO₂ circulating fluidinto a combustor, combusting the fuel to provide a combustion productstream comprising CO₂, expanding the combustion product stream across aturbine to generate power and output a turbine discharge stream,processing the turbine discharge stream to recycle at least a portion ofthe CO₂ circulating fluid into the combustor, withdrawing a portion ofthe CO₂ circulating fluid that is recycled, and using the recycled CO₂circulating fluid as a transpiration fluid.

Using the recycled CO₂ circulating fluid as the transpiration fluid maycomprise transpiring the recycled CO₂ circulating fluid in the turbine.Using the recycled CO₂ circulating fluid as the transpiration fluid maycomprise transpiring the recycled CO₂ circulating in the combustor. Themethod may further comprise directing the combustion product stream fromthe combustor through a conduit to the turbine, and using the recycledCO₂ circulating fluid as the transpiration fluid may comprisetranspiring the recycled CO₂ circulating fluid in the conduit. Themethod may also include conditioning the recycled CO₂ circulating fluidto a temperature that is less than a temperature of the combustionproduct stream. The method may additionally include conditioning therecycled CO₂ circulating fluid to a temperature that is substantiallyequal to a temperature of the combustion product stream. Also, themethod may include conditioning the recycled CO₂ circulating fluid to atemperature that is greater than a temperature of the combustion productstream.

In another embodiment a power generation system is provided. The systemmay comprise: a combustor configured for receiving a fuel, O₂, and a CO₂circulating fluid stream and having at least one combustion stage thatcombusts the fuel in the presence of the CO₂ circulating fluid stream soas to provide a combustion product stream comprising CO₂; a turbine influid communication with the combustor, the turbine having an inlet forreceiving the combustion product stream, an outlet for release of aturbine discharge stream comprising CO₂, and a plurality of turbineblades, wherein the combustion product stream acts on the turbine bladesto rotate the turbine and generate power; and one or more componentsconfigured for processing the turbine discharge stream to form arecycled CO₂ circulating fluid stream; wherein one or more components ofthe system are configured for using a portion of the recycled CO₂circulating fluid stream as a transpiration fluid.

The one or more components configured for processing the turbinedischarge stream to form the recycled CO₂ circulating fluid stream maycomprise a filter, a heat exchanger, a separator, and/or a compressor.The one or more components configured for using the portion of therecycled CO₂ circulating fluid stream as the transpiration fluid maycomprise a porous sintered material configured for receiving thetranspiration fluid therethrough. The turbine blades may have a bladeheight less than about 0.275 m. The turbine may comprise less than 2000of the turbine blades. A ratio of a length of the turbine to an averagediameter of the blades may be greater than 4.

In another embodiment a turbine assembly is provided. The assembly maycomprise a plurality of components including a casing defining an inletconfigured to receive a combustion product stream, and an outlet. Thecomponents may further comprise a rotor positioned in the casing, and aplurality of blades extending from the rotor, wherein one or more of thecomponents comprise a porous sintered material, the porous sinteredmaterial configured to direct a transpiration fluid therethrough.

The porous sintered material may define the entirety of the exteriorsurface of the blades. The casing may comprise the porous sinteredmaterial and the porous sintered material may be configured to directthe transpiration fluid to an interior surface of the casing. The rotormay comprise the porous sintered material and the porous sinteredmaterial may be configured to direct the transpiration fluid to anexterior surface of the rotor. The rotor may comprise an annular flowdiverter configured to divert the combustion product stream around therotor. The assembly may further comprise an inlet conduit coupled to theinlet of the casing and configured to couple to an outlet of a combustorassembly and receive the combustion product stream therefrom, and theinlet conduit may comprise the porous sintered material and the poroussintered material may be configured to direct the transpiration fluid toan interior surface of the inlet conduit. The inlet of the casing may beconfigured to couple directly to an outlet of a combustor assembly. Theinlet of the casing may be configured to receive the combustion productstream from a plurality of combustors radially disposed with respect toa major axis defined by the rotor.

The blades may comprise the porous sintered material, and the poroussintered material may be configured to direct the transpiration fluid toan exterior surface of the blades. The blades may respectively furthercomprise at least one reinforcement member. The reinforcement member maycomprise a rod that extends through the porous sintered material in eachof the blades. The reinforcement member may comprise a core, and theporous sintered material may extend around the core. The core may defineone or more channels configured to receive the transpiration fluid anddirect the transpiration fluid into the porous sintered material. One ormore channels may be defined in the blades, and the channels may beconfigured to receive the transpiration fluid and direct thetranspiration fluid into the porous sintered material. Each of theblades may extend from a leading edge to a trailing edge, and the bladesmay be configured to define a flow of the transpiration fluid at theleading edge that is greater than a flow of the transpiration fluid atthe trailing edge. Each of the blades may define a transpiration fluidinlet area at the leading edge that is greater than a transpirationfluid inlet area at the trailing edge. Each of the blades may define awall thickness that is greater at the trailing edge than at the leadingedge. Each of the blades may extend from a root at the rotor to a tip,and the porous sintered material may define a porosity that variesbetween the root and the tip. The porosity of the porous sinteredmaterial may be configured to define a flow of the transpiration fluidat the tip that is greater than a flow of the transpiration fluid at theroot. The porosity of the porous sintered material may be configured todefine a flow of the transpiration fluid at the tip that issubstantially equal to a flow of the transpiration fluid at the root.The porous sintered material may define a plurality of layers, whereinthe porosity of the layers increases from the root to the tip. Theblades may each respectively define an integral structure comprising aplurality of internal ribs.

The components of the turbine assembly may further comprise a pluralityof stators, wherein the stators comprise the porous sintered materialand the porous sintered material may be configured to direct thetranspiration fluid to an exterior surface of the stators. The turbineassembly may further comprise one or more seals, wherein one or more ofthe components are configured to direct the transpiration fluid to theseals. The seals may comprise the porous sintered material.

In another embodiment a turbine assembly is provided. The turbineassembly may comprise a casing defining an inlet configured to receive acombustion product stream, and an outlet. The assembly may furthercomprise a rotor positioned in the casing, and a plurality of bladesextending from the rotor, wherein a ratio of a length of the turbineassembly to the average diameter of the plurality of blades is greaterthan 4.

The turbine blades may have a blade height less than about 0.275 m. Theturbine assembly may comprise less than 2000 of the blades. The bladesmay be transpiration protected. Further, the blades comprise a poroussintered material configured to direct a transpiration fluid to anexterior surface of the blades.

Other aspects and advantages of the present invention will becomeapparent from the following.

BRIEF DESCRIPTION OF THE FIGURES

Having thus described the disclosure in general terms, reference willnow be made to the accompanying figures, wherein:

FIG. 1 provides a flow diagram of a combustion cycle and systemaccording to one example embodiment;

FIG. 2 provides a flow diagram of a combustion cycle and systemaccording to a further example embodiment;

FIG. 3 provides a sectional view through a combustor in accordance withone example embodiment;

FIG. 4 provides a sectional view through a turbine including an inletconduit in accordance with one example embodiment;

FIG. 5 provides a longitudinal sectional view through a turbine and aplurality of radially disposed combustors in accordance with one exampleembodiment;

FIG. 6 provides a lateral sectional view through the turbine andcombustor system of FIG. 5;

FIG. 7 provides a lateral sectional view through a turbine including acore in accordance with one example embodiment;

FIG. 8 provides a partial sectional view through an inlet conduitcomprising first and second layers in accordance with one exampleembodiment;

FIG. 9 provides a partial sectional view through an inlet conduitcomprising four layers in accordance with one example embodiment;

FIG. 10 provides a sectional view between the leading and trailing edgesof a turbine blade comprising reinforcement rods and channels configuredto receive a transpiration fluid in accordance with one exampleembodiment;

FIG. 11 illustrates a sectional view between a leading edge and atrailing edge of a turbine blade including integral internal ribsdefining channels configured to receive a transpiration fluid inaccordance with one example embodiment;

FIG. 12 illustrates a sectional view between the tip and base member ofthe turbine blade of FIG. 11;

FIG. 13 illustrates a perspective view of the turbine blade of FIG. 11;

FIG. 14 illustrates a sectional view between a leading edge and atrailing edge of a turbine blade defining differing material thicknessesbetween the leading and trailing edges in accordance with one exampleembodiment;

FIG. 15A illustrates a partial sectional view between the root and tipof a turbine blade including layers of material defining differingporosities between the root and tip in accordance with one exampleembodiment;

FIG. 15B illustrates a partial sectional view between the root and tipof a turbine blade defining a porosity gradient between the root and tipin accordance with one example embodiment;

FIG. 16 illustrates a calculated particle trajectory for a particle in aturbine in accordance with one example embodiment;

FIG. 17 provides a graphical illustration of radial travel distance ofparticulates in a combustion product flow in a combustor as a functionof axial travel distance in accordance with one example embodiment;

FIG. 18 illustrates a lengthwise cross-section of a conventional turbinefor use in conventional natural gas power plant; and

FIG. 19 illustrates a lengthwise cross-section of a turbine according toexample embodiments that is generally smaller in size than aconventional turbine.

DETAILED DESCRIPTION

The disclosure now will be described more fully hereinafter throughreference to various embodiments. These embodiments are provided so thatthis disclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art. Indeed, thedisclosure may be embodied in many different forms and should not beconstrued as limited to the embodiments set forth herein; rather, theseembodiments are provided so that this disclosure will satisfy applicablelegal requirements. As used in the specification, and in the appendedclaims, the singular forms “a”, “an”, “the”, include plural referentsunless the context clearly dictates otherwise.

The present disclosure in one embodiment relates to turbine bladedesigns and methods of use that can reduce or even eliminate turbineblade erosion arising from chemical degradation by air or steam or byparticle impingement. The disclosure also provides power productionmethods and systems that can provide high efficiency operation whilereducing or even eliminating turbine blade erosion arising fromparticulates in a combustion product flow without the requirement offiltration prior to passage through the turbine. The reduction and/orelimination of blade erosion can simplify power production systems andincrease possible feedstocks since it allows for the turbines to processcombustion product flow with higher total particulate concentration andis thus particularly beneficial in combustion processes usingfeedstocks, such as coal, that include a relatively high concentrationof particulates in the combustion product.

The terms “particulates” and “particles” (including such terms in thesingular form) as used in relation to components of the combustionproduct stream specifically encompass solid and liquid materials presentin the combustion product stream in a relatively small unit sizetypically understood to be characteristic of particles, specifically inrelation to the overall volume of the combustion product stream. In someembodiments, particles or particulates may comprise any material in thecombustion product stream that is in a non-gaseous state. Liquidparticulates specifically may encompass materials that are liquid at thetemperature of the combustion product stream but that are solid at atemperature that is less than the temperature of the combustion productstream, such as at least 10° C., at least 15° C., at least 20° C., atleast 30° C., at least 50° C., or at least 100° C. less than thetemperature of the combustion product stream. Such liquid particulatesmay have a freezing point that is at least ambient temperature, at leastabout 40° C., at least about 50° C., at least about 60° C., at leastabout 80° C., at least about 100° C., or at least about 200° C. Inspecific embodiments, the liquid particles may have a freezing pointfalling within any combination of the above-listed temperatures (e.g.,within the range that is at least 10° C. less than the temperature ofthe combustion product stream and at least ambient temperature).

In particular embodiments, the present disclosure realizes that particleimpact damage on turbine blades is related to blade velocity. Inparticular, a damage rate arising from particle impact can change asapproximately the cube of blade velocity relative to particle velocity.In this regard, the standard alternating current frequency employed inthe United States is 60 Hz. Further, power production systems in theUnited States typically drive synchronous alternating current generatorsthat operate at either 1,800 rpm (30×60 Hz) or 3,600 rpm (60×60 Hz),although it should be understood that the turbines may rotate withinother rpm ranges. In this regard, other countries may employ differingstandard alternative current frequencies. For example, the UnitedKingdom operates at a frequency of 50 Hz. Further, generator systems mayemploy permanent magnet direct current generators driven at any speedsuch that the direct current is converted to alternating current havinga desired frequency. Accordingly, it should be understood that thefrequencies discussed herein are provided for example purposes only.

However, known gas turbines used in power production systems and methodsincluding synchronous alternating current generators typically operateat blade speeds of 600 mph (268 m/s) or greater. At blade speeds typicalin existing steam and gas turbines, the presence of even very smallparticulates in a combustion product flow can cause blade erosion. Thepresent disclosure, however, has recognized the ability to overcomeblade erosion through alterations in blade structure and operation thatallows for decreased blade velocities. In specific embodiments, bladevelocity according to the present disclosure may be from about 20 m/s toabout 340 m/s at the blade tip. More specifically, the blade velocitymay be below 200 m/s, below 100 m/s, or from about 50 m/s to about 75m/s. In one embodiment, the disclosure can provide for turbine operationat a blade velocity that is about 3 times lower than typical (i.e., 200mph (89 m/s)), which may result in a decrease in blade erosion rate of27 fold or more. In one embodiment, a blade velocity of 150 mph (67m/s)—i.e., a four-fold decrease from typical blade velocities—canprovide approximately a 64 fold decrease in blade damage rate.

The ability to operate the turbine in a power production system at alower velocity can arise from a variety of factors that can be embodiedsingularly or in multiple combinations. For example, the turbine bladescan be designed with dimensions that can allow for the blade velocity tobe slowed to a speed where particle impingement no longer causes erosionof the turbine blades. More specifically, the operating blade speed canbe reduced below the critical velocity at which erosion occurs. In thisregard, the blade speed at any given point on a blade is provided by thefollowing formula:

v=(rpm/60)*2*π*r  (Formula 1)

where:

-   -   v=blade speed (m/s),    -   rpm=rotations of the blade per minute,    -   π=pi, and    -   r=distance (m) between a center of the rotor and a point on the        blade at which the blade velocity is to be determined (e.g.,        radius).

Note further that the blade speed at the tip of a blade is provided bythe following formula:

v _(t)=(rpm/60)*2*π*(a+b)  (Formula 2)

where:

-   -   v_(t)=blade speed (m/s) at the tip of the blade,    -   rpm=rotations of the blade per minute,    -   π=pi,    -   a=radius (m) of the rotor at the blade, and    -   b=blade height (m).

Thus, the maximum blade speed for each blade may be reduced bydecreasing the distance to which the blades extend from the center ofthe rotor. As discussed below, use of turbines having blades extendingto relatively smaller radii may be enabled by employing a supercriticalfluid having relatively high fluid density and high pressure at amoderate flow velocity in the turbine of the present disclosure.Further, employing a high density working fluid in the turbine mayprovide for significantly reduced turbine blade temperature by improvingthe ability of transpiration to cool the blades.

Blade height (i.e., the distance from a root at the outer surface of theturbine shaft (e.g. rotor) to the blade tip) preferably is less thanabout 0.275 m. In specific embodiments, average blade height can beabout 0.05 m to about 0.25 m, about 0.075 m to about 0.225 m, about 0.1m to about 0.2 m, or about 0.125 m to about 0.175 m. In specificembodiments, actual blade heights could vary from the turbine inlet tothe turbine outlet. For example, blade height at the inlet could belower than the average and increase toward the outlet such that bladeheight at the outlet is higher than the average. Average blade width canbe about 0.025 m to about 0.125 m, about 0.04 m to about 0.11 m, about0.05 m to about 0.1 m, or about 0.06 m to about 0.09 m. In otherembodiments, blade height and width can be further dimensions that allowfor operation at a velocity as described herein.

The inventive turbines and methods of operation also can becharacterized by overall turbine dimensions. For example, a turbineaccording to the disclosure can have an overall length of less thanabout 11 m, less than about 10 m, or less than about 9 m. In furtherembodiments, overall turbine length can be about 6 m to about 10 m,about 6.5 m to about 9.5 m, about 7 m to about 9 m, or about 7.5 m toabout 8.5 m. A turbine according to the disclosure can have an averagediameter of less than about 3.5 m, less than about 3 n, or less thanabout 2.5 m. In further embodiments, average turbine diameter can beabout 0.25 m to about 3 m, about 0.5 m to about 2 m, or about 0.5 m toabout 1.5 m. The ratio of turbine length to turbine average diameter(i.e., diameter of the turbine blades) can be greater than about 3.5,greater than about 4, greater than about 4.5, or greater than about 5.In specific embodiments, the ratio of turbine length to turbine averagediameter can be about 3.5 to about 7.5, about 4 to about 7, about 4.5 toabout 6.5, or about 5 to about 6. The above ratios specifically canrelate to the total length of the turbine. In some embodiments, totallength may refer to the length of the casing from inlet to outlet. Incertain embodiments, total length may refer to the distance within thecasing from the turbine blade immediately adjacent the inlet to theturbine blade immediately adjacent the outlet.

The inventive turbines and methods of operation likewise can becharacterized by average blade radius (center of the rotor to tip of theturbine blade). Preferably, the turbines operate with an average bladeradius of less than about 1.2 m, less than about 1.1 in, less than about1 m, less than about 0.9 m, less than about 0.8 m, less than about 0.7m, or less than about 0.6 m. Turbine blade radius specifically can beabout 0.25 m to about 1 m, about 0.275 m to about 0.8 m, about 0.3 m toabout 0.7 m, about 0.325 m to about 0.6 m, about 0.35 m to about 0.5 m,or about 0.375 m to about 0.475 m.

In certain embodiments, a turbine useful according to the disclosure canhave a total number of turbine blades that is significantly less thanpresent in typical gas turbine systems. Specifically, the inventiveturbines may have less than about 3,000 blades, less than about 2,500blades, or less than about 2,000 blades. In further embodiments, thenumber of blades in a turbine can be about 500 to about 2,500, about 750to about 2,250, about 1,000 to about 2,000, or about 1,250 to about1,750.

In some embodiments, the turbines according to the disclosureparticularly can provide high efficiency power production with reducedblade velocity through operation at significantly increased inletpressure, and/or significantly increased outlet pressure, and/orsignificantly increased pressure drop from inlet to outlet in relationto typical gas turbine power production systems. In specificembodiments, the turbine can be operated at an inlet pressure of atleast about 25 bars (2.5 MPa), at least about 50 bars (5 MPa), at leastabout 100 bars (10 MPa), at least about 150 bars (15 MPa), at leastabout 200 bars (20 MPa), or at least about 250 bars (25 MPa). In furtherembodiments, inlet pressure can be about 50 bars (5 MPa) to about 500bars (50 MPa), about 100 bars (10 MPa) to about 450 bars (45 MPa), about150 bars (15 MPa) to about 400 bars (40 MPa), about 200 bars (20 MPa) toabout 400 bars (40 MPa), or about 250 bars (25 MPa) to about 350 bars(35 MPa).

In further embodiments, the turbine can be operated with an outletpressure of at least about 5 bars (0.5 MPa), at least about 10 bars (1MPa), at least about 15 bars (1.5 MPa), at least about 20 bars (2 MPa),or at least about 25 bars (2.5 MPa). The outlet pressure particularlymay be about 10 bars (1 MPa) to about 50 bars (5 MPa), about 15 bars(1.5 MPa) to about 45 bars (4.5 MPa), about 20 bars (2 MPa) to about 40bars (4 MPa), or about 25 bars (2.5 MPa) to about 35 bars (3.5 MPa).

In other embodiments, the ratio of turbine inlet pressure to turbineoutlet pressure can be at least about 6, at least about 7, at leastabout 8, at least about 9, or at least about 10. In specificembodiments, the ratio of turbine inlet pressure to turbine outletpressure can be about 6 to about 15, about 7 to about 14, about 8 toabout 12, or about 9 to about 11.

In yet other embodiments, the turbines according to the disclosure canbe operated in a power production system at a significantly increasedflow density in relation to operation of turbines in typical powerproduction systems. For example, the inventive turbines can be operatedat a flow density of at least about 20 kg/m³, at least about 50 kg/m³,at least about 100 kg/m³, at least about 150 kg/m³, at least about 200kg/m³, or at least about 300 kg/m³, at least about 400 kg/m³, at leastabout 500 kg/m³, or at least about 600 kg/m³.

In contrast to the turbines in accordance with the present disclosure,existing gas turbine compressors may operate with outlet pressures fromabout 1 Bar (0.1 MPa) to about 15 Bar (1.5 MPa), with gas densities inthe compressor section ranging from 1 kg/m³ to about 15 kg/m³ (assumingadiabatic compression heating). Erosion and other problems may not besevere in the compressor due to the relatively low temperatures therein.However, in the hot section, the gas temperature may vary from a peak ofroughly 1727° C. to about 527° C. The density of the gas in the hotsection may vary from a high of about 5 kg/m³ to a low of about 0.5kg/m³. Thus, the conditions inside existing turbines may varyconsiderably from those within the turbines in accordance with thepresent disclosure.

The use of higher pressures at lower flow rates and higher temperaturesmay increase the torque on the turbine blades. Accordingly, the turbinemay include features configured to reduce the torque applied to theblades. In particular, the turbine may include a larger number ofblades, discs, and/or stages than conventional turbines, whichdistributes the torque therebetween to reduce the torque applied to theindividual blades. Further, the blades may define an angle of attackconfigured to exert less force and torque on the blades. In particular,the blades may define a decreased angle with respect to the flow throughthe turbine, which induces less drag and increases the lift to dragratio. Accordingly, these features may reduce the torque exerted on eachof the blades so that they may be formed from relatively less strong andrelatively less expensive materials.

In some embodiments, blade erosion also may be controlled, reduced, oreliminated by combining any of the above-described characteristics withone or more methods of blade cooling. Any method of turbine bladecooling could be combined with the present disclosure, includingtranspiration blade cooling, as more fully described below. In thisregard, transpiration cooling may be employed to cool any of the variouscomponents of the turbine, combustor, and related apparatuses disclosedherein. With particular regard to the turbine, the case, stators (e.g.,stator blades), seals, blades (e.g., turbine blades), rotor, and variousother internal components may be transpiration cooled through, forexample, employing the porous materials disclosed herein. In thisregard, the stators may comprise the porous sintered material and theporous sintered material may be configured to direct the transpirationfluid to an exterior surface of the stators. Additionally, one or moreof the components of the turbine assembly may be configured to directtranspiration fluid to the seals. The seals may comprise the poroussintered material in some embodiments. Example embodiments of seals andstators that may be transpiration cooled in accordance with embodimentsof the disclosure are described in U.S. Pat. App. Pub. 2009/0142187,which is incorporated herein by reference in its entirety. However,various other embodiments of components of turbines, combustors, andrelated apparatuses may also be transpiration cooled in accordance withthe present disclosure.

Further, the transpiration cooling techniques disclosed herein mayprovide improved cooling relative to existing transpiration coolingtechniques. Current blade cooling is typically conducted with bleed airfrom the compressor of the turbine. This air has a limited heat capacitydue to its relatively low density (e.g., 0.5-5 kg/m³) set by therelatively low operating pressure of the turbine hot section in existingturbines, as described above. This limits the heat transfer rates. Incontrast, as discussed below, the present disclosure provides fortranspiration cooling through use of CO₂, which may provide improvedheat transfer.

The heat transfer rates for existing embodiments of turbines are alsolimited by the relatively large stress placed on the turbine blades dueto the long length of the blades resulting in high centrifugal forcesduring rotation thereof. The cooling passages in existing turbines thusmust be kept relatively small and they must not define more than arelatively small fraction of the blade overall cross-sectional area inorder to limit the reduction in longitudinal strength of the bladescaused by the cooling passages.

The inventive turbines are particularly useful in systems and methodsfor power production in that the turbines not only provide for reducedblade erosion but also can significantly reduce total turbine cost. Inspecific embodiments, total turbine cost in relation to turbines used intypical power production systems can be reduced by at least 20%, atleast 30%, at least 40%, at least 50%, at least 60%, at least 70%, or atleast 75% without any significant loss in electrical power output (i.e.,loss of less than 5%, less than 4%, less than 3%, less than 2%, lessthan 1%, or less than 0.8%). Reductions in cost may occur by avoidingthe need for superalloys and/or other expensive materials in the bladesdue, for example, to a reduction in the centrifugal forces appliedthereto. Further, reductions in power output may be minimized despitereduced rotating speeds by employing high inlet temperatures in theturbine as well as high operating pressures relative to existingembodiments of turbines.

In specific embodiments, the present disclosure can comprise systems andmethods for power production that can incorporate the present turbineblade designs and modes of operation. For example, the inventive systemsand methods allow for power production through use of a high efficiencyfuel combustor (such as a transpiration cooled combustor), optionallywith an associated circulating fluid (such as a CO₂ circulating fluid).Specifically, the use of a high pressure circulating fluid (or workingfluid) that has a high CO₂ recycle ratio provides the ability to directa portion of the CO₂ circulating fluid to the turbine blades fortranspiration cooling.

The combination of transpiration cooling with the blade designs andmodes of operation of the present disclosure particularly can be usefulsince erosion can be a function of turbine blade temperature and bladematerial composition. The combination of turbine blade design andoperation with blade operation temperature can provide for a wide rangeof possible blade operation velocities and blade operation temperatureswherein blade erosion can be controlled, reduced, or eliminated. Atlower blade temperatures, erosion is lower, and the blade velocity atwhich erosion starts can be higher. The ability to choose operationconditions is beneficial in that it can allow for the use of metalalloys that can resist erosion at higher blade velocities but otherwisewould not be available for use at higher operating temperatures. In thisregard, at lower temperatures, high strength steels are relativelyimmune to impact damages. As an example, rolled homogenous armor used onmilitary vehicles is not damaged by solid steel bullets traveling at upto speeds of 400 mph (179 m/s).

In other embodiments, however, as more fully described below,transpiration may effect blade protection by preventing solidificationof combustion product stream components (e.g., liquid ash). In suchembodiments, transpiration cooling may be defined as cooling the blades(and/or other components) to a temperature below the temperature of thecombustion product stream. More particularly, such cooling may beconfigured to have a lower limit that is greater than the temperature atwhich a component of the combustion product stream (e.g., liquid ash)will freeze (or solidify) and thus become deposited upon the turbineblades. For example, ash softening may begin at 590° C., and melting mayoccur at 870° C. Without transpiration cooling, the turbine would needto operate well below 590° C. to avoid ash buildup on the blades, whichis too low for efficient operation. With transpiration protection, theturbine can operate above 870° C., where the ash is liquid, but theliquid droplets do not touch or stick to the surface because of thetranspiration vapor layer covering substantially all surfaces that areinternal to the turbine and thus subject to contact with components of astream flowing through the turbine (e.g., the internal surface of theturbine housing, the external surfaces of the turbine blades within theturbine, etc.). Thus, transpiration protection may reduce or eliminatenot only degradation due to mechanical erosion by particle impingement,but also chemical degradation by keeping the blades cooler, and byreplacing air or air/steam as the coolant with CO₂ as the coolant in theform of a transpiration fluid.

In some embodiments, it can be useful for the turbines to be operated atblade velocities that are relative to the velocity of the combustionproduct flow. In such embodiments, it can be particularly beneficial forflow velocity to be significantly less than flow velocities in typicalcombustion processes. For example, flow velocity according to thedisclosure can be less than about 400 mph (179 m/s), less than about 350mph (156 m/s), less than about 300 mph (134 m/s), less than about 250mph (112 m/s), less than about 200 mph (89 m/s), less than about 150 mph(67 m/s), or less than about 100 mph (45 m/s). The ratio of blade tipvelocity to flow velocity preferably is greater than 1, greater than1.5, greater than 2, greater than 2.5, or greater than 3. Specifically,the ratio of blade tip velocity to flow velocity can be about 1 to about5, about 1.5 to about 4.75, about 1.75 to about 4.5, about 2 to about4.25, or about 2.5 to about 4.

As a result of erosion, turbines may experience degradation inperformance over time (e.g., through reduced efficiency and/or poweroutput). For example, a conventional turbine may experience operationaldegradation of 10% power loss over a two to three year period. Anoverhaul to repair the turbine may cost approximately 50% of thepurchase cost of the turbine. Accordingly, over a 20 year lifetime,existing turbines may be overhauled a total of eight times, which maycost a total of 4 times the initial purchase price of the turbine.

This degradation may be due to erosion caused by residual dust particlesthat get past an air filtration system positioned between the combustorand the turbine. Increasing the particulate removal effectiveness of thefilters may not be a viable option because this may restrict air flowand reduce efficiency of the turbine. Thus, the turbines of the presentdisclosure may provide significant cost savings by minimizing oreliminating the need for overhauls by minimizing or eliminating damagefrom erosion. In this regard, the rate of dissipation of impact energyassociated with collision between the particles and blades isapproximately proportional to the cube of the relative velocitytherebetween. In this regard, erosion of turbine blades tends to beapproximately proportional to the rate of impact energy dissipation(“Impact Power”), as illustrated below:

IP: kV ³ /X  (Formula 3)

where:

-   -   IP=impact power,    -   k=a variable factor based on the particle material, the blade        material, the ambient temperature, and the impact angle,    -   v=relative velocity between the turbine blades and particles,        and    -   X=characteristic length of the impact interaction.

By reducing the speed of the blades and providing transpirationprotection, impacts may be minimized or reduced below a threshold atwhich erosion occurs and chemical damage may also be reduced oreliminated. Accordingly, expenses associated with overhauls due toerosion may be reduced or eliminated, and thus embodiments of theturbines provided herein may provide significant cost savings. Further,as noted above, by eliminating the need for use of expensivesuperalloys, the turbines in accordance with the present disclosure maybe relatively less expensive than existing turbines.

In various known embodiments of power plants, efficiency is criticallydependent on turbine inlet temperatures. For example, extensive work hasbeen done at great cost to achieve turbine technology allowing for inlettemperatures as high as about 1,350° C. The higher the turbine inlettemperature, the higher the plant efficiency, but also the moreexpensive the turbine is, and potentially, the shorter its lifetime.Because of the relatively high temperature of the combustion productstream, it can be beneficial for the turbine to be formed of materialscapable of withstanding such temperatures. It also may be useful for theturbine to comprise a material that provides good chemical resistance tothe type of secondary materials that may be present in the combustionproduct stream.

In certain embodiments, the present disclosure can particularly providefor the use of a cooling fluid with the turbine components. As morefully described below, for example, the inventive systems and methodsallow for power production through use of a high efficiency fuelcombustor (e.g., a transpiration cooled combustor) and an associatedcirculating fluid (such as a CO₂ circulating fluid). Specifically, aportion of the circulating fluid can be directed to the turbinecomponents, particularly the turbine blades, to be used in turbinecooling, such as through transpiration cooling.

For example, in some embodiments, a portion of a CO₂ circulating fluidcan be withdrawn from the cycle (e.g., from a portion of the cycle wherethe circulating fluid is under conditions useful for a transpirationcooling fluid) and directed to a turbine for cooling of the components,particularly the turbine blades. The blade cooling fluid can bedischarged from holes (or perforations) in the turbine blade and beinput directly into the turbine flow. Thus, rather than using air as atranspiration cooling fluid (which is limited in its cooling ability asdescribed above, and hampered by safety concerns), the methods andsystems of the disclosure provide for the use of very large quantitiesof high pressure CO₂, supercritical CO₂, and even liquid CO₂ as aturbine blade cooling medium. This is highly useful because it increasesthe cooling capacity available for the turbine blades by large ratios inrelation to known blade cooling methods. The disclosure also isparticularly useful because the CO₂ circulating fluid can be present inthe system in very large quantities, which allows for a very largequantity of cooling fluid to be moved through the turbine blades. Thishigh volume and/or high mass flow of CO₂ cooling fluid through theturbine blades not only protects the turbine blades from the extremeheat that is useful for high efficiency power production methods, but italso assists in protecting the turbine blades from the corrosive anderosive effects of the high temperature gases and unfiltered particulatematerial flowing through the turbine by transpiration of the CO₂ coolingfluid out through the entire surface of the blade. In one embodimenttranspiration cooling may provide for operational blade temperaturesfrom about 200° C. to about 700° C. despite the significantly higherturbine inlet temperatures described above (e.g., 1350° C.), which maythus allow for use of turbine blades comprising relatively lessexpensive materials than those which are presently employed and/orhigher turbine inlet temperatures may be employed, which may lead togreater efficiency. The foregoing transpiration cooled turbinecomponents can be used in any power production method and system whereinhigh pressure CO₂ (or other fluid which is less corrosive than air orsteam, such as N₂) can be made available as a high recycle ratiocirculating fluid.

In specific embodiments, the use of a CO₂ circulating fluid as a turbineblade cooling medium allows for the turbine blades to be fabricated frommuch lower cost materials than known turbine blades used in highefficiency power production methods because use of the CO₂ coolingmedium prevents the blades in the present disclosure from being heatedto the extreme temperatures of the surrounding combustion product flowand reduces the corrosive and erosive effects of the combustion productflow. For example, according to the present disclosure, turbine bladescould be fabricated from a wide variety of high strength steels, or evenrelatively low cost steels. Likewise, the blades could be fabricatedfrom carbon composites or even low temperature materials, such asaluminum. Any material recognized as useful in the art for gas turbinecomponents, even for turbines used in low temperature conditions and/orlow erosive or low corrosive conditions, could be used for fabricatingturbine components according to the present disclosure.

Transpiration cooling of turbine blades with a portion of a CO₂circulating fluid according to the present disclosure further is usefulbecause it can facilitate the safe passage of combustion gassescontaining ash (or other particulate matter and/or incombustibles)through the turbine without the need for an intervening filtration stepand component. This can greatly simplify the design of power productionfacilities and increase the types of materials that may be used as thefuel source for combustion.

The use of a CO₂ circulating fluid in transpiration cooling of turbinecomponents according to the present disclosure also is advantageous inrelation to the thermodynamics of the power production cycle. Because ofthe vastly improved cooling ability of the CO₂ circulating fluid inrelation to known transpiration media for turbine blades, it is possibleto operate the combustor at increased temperatures without thelimitation of the heat tolerance of the turbine. Thus, combustorscapable of operation at extremely high temperatures (e.g., transpirationcooled combustors) can be operated according to the present disclosureat near maximum operating temperatures since the combustion product flowcan be passed through the CO₂ cooled turbine without damage to theturbine components. This increases the potential thermodynamicefficiency of the power production cycle to approaching 100%.

Any combination of turbine blade design, overall turbine design, andtranspiration cooling of the turbine blades can be used in any powerproduction method where turbine blade life is desirably extended, suchas methods and systems where combustion results in formation ofparticulates. In some embodiments, the methods and systems particularlycan be those wherein a circulating fluid can be used. For example, highpressure CO₂ can be made available as a high recycle ratio circulatingfluid.

For example, a turbine as described herein may be used in a method andsystem wherein a CO₂ circulating fluid is provided in a combustor alongwith an appropriate fuel, any necessary oxidant, and any associatedmaterials that may be useful for efficient combustion. Such systems andmethods can comprise a combustor that operates at very high temperatures(e.g., in the range of about 1,600° C. to about 3,300° C., or evengreater), and the presence of the circulating fluid can function tomoderate the temperature of a fluid stream exiting the combustor so thatthe fluid stream can be utilized in energy transfer for powerproduction. Specifically, a combustion product stream can be expandedacross at least one turbine to generate power. The expanded gas streamcan be cooled to remove various components from the stream, such aswater, and heat withdrawn from the expanded gas stream can be used toheat the CO₂ circulating fluid. The purified circulating fluid streamcan then be pressurized and heated for recycle through the combustor.Exemplary power production systems and methods that may incorporate theturbine blade designs of the present disclosure (with or withoutassociated blade transpiration cooling) are described in U.S. Pat. App.Pub. 2011/0179799, which is incorporated herein by reference in itsentirety.

The incorporation of a turbine according to the disclosure in acombustion power cycle is particularly useful in relation to combustionof fuels that result in a particulate component. Various types of coal,for example, can be combusted in a power production cycle to produce acombustion stream having a content of ash and/or other particulates.Beneficially, when a turbine according to the disclosure is incorporatedinto the combustion cycle, the full combustion product stream (i.e.,including the full content of particulates) can be introduced into theturbine without the need of a preliminary filtering step. This enablesthe use of higher turbine inlet temperature which in turn increasescombustion efficiency in relation to processes requiring filtration ofthe combustion product prior to passage through the turbine. This ispossible according to the disclosure since the inventive turbines can besubjected to particle impingement without significant erosion.Particulate materials then can be filtered from the stream exiting theturbine.

One embodiment of a combustion cycle provided according to the presentdisclosure is illustrated in the flow diagram of FIG. 1. In theillustrated embodiment, an air separation unit 100 is provided to intakeambient air 10 and output an enriched oxygen stream 120. The oxygenstream 120 may comprise oxygen having a molar purity of at least about50%, at least about 60%, at least about 70%, at least about 80%, atleast about 85%, at least about 90%, or at least about 95%. The oxygenstream 120 may be supplied, for example, by any air separationsystem/technique known in the art, such as, for example, a cryogenic airseparation process, or a high temperature ion transport membrane oxygenseparation process (from air), could be implemented. In specificembodiments, an enriched oxygen stream may be produced by the operationof a cryogenic air separation process in which the oxygen is pressurizedin the process by pumping liquid oxygen that is efficiently heated toambient temperature conserving refrigeration. Such a cryogenic pumpedoxygen plant can have two air compressors, both of which can be operatedadiabatically with no inter-stage cooling. In specific embodiments, itmay be useful to include components useful for recovering heat producedby the air separation unit and transferring the heat to a component ofthe presently described system where heat input may be desirable.

The cycle illustrated in FIG. 1 can be useful for combustion of any fuelsource that includes particulate matter (e.g., ash) as a component ofthe combustion product. Non-limiting examples of fuels that are usefulaccording to the disclosure include various grades and types of coal,wood, oil, tar from tar sands, bitumen, biomass, algae, gradedcombustible solid waste refuse, asphalt, and used tires. In particular,any solid fuel material may be used in the disclosure, and such fuelsparticularly may be ground, shredded, or otherwise processed to reduceparticles sizes, as appropriate. A fluidization or slurrying medium canbe added, as necessary, to achieve a suitable form and to meet flowrequirements for high pressure pumping. For example, referring to FIG.1, the solid fuel 15 can be passed through a mill apparatus 200 toprovide a powdered fuel. In other embodiments, the solid fuel 15 couldbe provided in a particularized condition to forego the need for on-sitemilling. In specific embodiments, the solid fuel 15 may have an averageparticle size of about 10 μm to about 500 μm, about 25 μm to about 400μm, or about 50 μm to about 200 μm. In other embodiments, the solid fuel15 may be described in that greater than 50%, 60%, 70%, 80%, 90%/o, 95%,or 99% of the solid fuel particles have an average size of less thanabout 500 μm, 400 μm, 300 μm, 200 μm, or 100 μm.

The solid fuel 15 can be suitably processed to allow for injection intoa combustion apparatus at sufficient rates and at pressures above thepressure within the combustion chamber. To provide such characteristic,the solid fuel 15 may be in liquid, slurry, gel, or paste form withappropriate fluidity and viscosity at ambient temperatures or atelevated temperatures. For example, the solid fuel 15 may be provided ata temperature of about 30° C. to about 500° C., about 40° C. to about450° C., about 50° C. to about 425° C., or about 75° C. to about 400° C.When the solid fuel 15 is in a ground, shredded, or otherwise processedcondition so that particle size is appropriately reduced, a fluidizationor slurrying medium can be added, as necessary, to achieve a suitableform and to meet flow requirements for high pressure pumping. Asillustrated in the embodiment of FIG. 1, the particulate solid fuel 220produced from the solid fuel 15S by the mill apparatus 200 can be mixedwith a fluidizing substance to provide the coal in the form of a slurry.In particular, the particulate solid fuel 220 is combined in a mixer 250with a CO side draw 562 from a recycled CO₂ circulating fluid stream561. The CO₂ side draw 562 may be provided in a supercritical, highdensity state. In specific embodiments, the CO₂ used to form the slurrycan have a density of about 450 kg/m³ to about 1,100 kg/m³. Moreparticularly, the CO₂ side draw 562 may cooperate with the particulatesolid fuel 220 to form a slurry 255 having, for example, from about 10weight % to about 75 weight % or from about 25 weight % to about 55weight % of the particulate coal. Moreover, the CO₂ from the side draw562 used to form the slurry 255 may be at a temperature of less thanabout 0° C., less than about −10° C., less than about −20° C., or lessthan about −30° C. In further embodiments, the CO₂ from the side draw562 used to form the slurry may be at a temperature of about 0° C. toabout −60° C., about −10° C. to about −50° C., or about −18° C. to about−40° C. Although the slurrying step is described in terms of using CO₂as a slurry medium, it is understood that other slurrying mediums couldbe used.

The slurry 255 can be transferred from the mixer 250 via a pump 270 to acombustion apparatus 300. In specific embodiments, the combustionapparatus 300 can be a high efficiency combustor capable of providingsubstantially complete combustion of a fuel at a relatively highcombustion temperature. High temperature combustion can be particularlyuseful to provide for substantially complete combustion of allcombustible components of the fuel and thus maximize efficiency. Invarious embodiments, high temperature combustion can mean combustion ata temperature of at least about 1,000° C., at least about 1,200° C., atleast about 1,500° C., at least about 2,000° C., or at least about3,000° C. In further embodiments, high temperature combustion can meancombustion at a temperature of about 1,000° C. to about 5,000° C. or,about 1,200° C. to about 3,000° C.

In certain embodiments, the combustion apparatus 300 may be atranspiration cooled combustor. One example of a transpiration cooledcombustor that may be used in the disclosure is described in U.S. Pat.App. Pub. No. 2010/0300063 and U.S. Pat. App. Pub. No. 2011/0083435, thedisclosures of which are incorporated herein by reference in theirentirety. In some embodiments, a transpiration cooled combustor usefulaccording to the disclosure may include one or more heat exchange zones,one or more cooling fluids, and one or more transpiration fluids.

The use of a transpiration cooled combustor according to the presentdisclosure is particularly advantageous over the known art around fuelcombustion for power production. For example, the use of transpirationcooling can be useful to prevent corrosion, fouling, and erosion in thecombustor. This further allows the combustor to work in a sufficientlyhigh temperature range to afford complete or at least substantiallycomplete combustion of the fuel that is used. These, and furtheradvantages, are further described herein.

In one particular aspect, a transpiration cooled combustor usefulaccording to the disclosure can include a combustion chamber at leastpartially defined by a transpiration member, wherein the transpirationmember is at least partially surrounded by a pressure containmentmember. The combustion chamber can have an inlet portion and an opposingoutlet portion. The inlet portion of the combustion chamber can beconfigured to receive the carbon containing fuel to be combusted withinthe combustion chamber at a combustion temperature to form a combustionproduct. The combustion chamber can be further configured to direct thecombustion product toward the outlet portion. The transpiration membercan be configured to direct a transpiration substance therethroughtoward the combustion chamber for buffering interaction between thecombustion product and the transpiration member. In addition, thetranspiration substance may be introduced into the combustion chamber toachieve a desired outlet temperature of the combustion product. Inparticular embodiments, the transpiration substance can at leastpartially comprise the circulating fluid. The walls of the combustionchamber may be lined with a layer of porous material through which thetranspiration substance, such as CO₂ and/or H₂O, is directed and flows.

The flow of the transpiration substance through this poroustranspiration layer, and optionally through additional provisions, canbe configured to achieve a desired total exit fluid stream outlettemperature from the combustion apparatus 300. In some embodiments, asfurther described herein, such temperature can be in the range of about500° C. to about 2,000° C. This flow may also serve to cool thetranspiration member to a temperature below the maximum allowableoperational temperature of the material forming the transpirationmember. The transpiration substance may also serve to preventimpingement of any liquid or solid ash materials or other contaminantsin the fuel which might corrode, foul, or otherwise damage the walls. Insuch instances, it may be desirable to use a material for thetranspiration member with a reasonable thermal conductivity so thatincident radiant heat can be conducted radially outwards through theporous transpiration member and then be intercepted by convective heattransfer from the surfaces of the porous layer structure to the fluidpassing radially inwards through the transpiration layer. Such aconfiguration may allow the subsequent part of the stream directedthrough the transpiration member to be heated to a temperature in adesirable range, such as about 500° C. to about 1,000° C. or from about200° C. to about 700° C., while simultaneously maintaining thetemperature of the porous transpiration member within the design rangeof the material used therefor. Suitable materials for the poroustranspiration member may include, for example, porous ceramics,refractory metal fiber mats, hole-drilled cylindrical sections, and/orsintered metal layers or sintered metal powders. A second function ofthe transpiration member may be to ensure a substantially even radiallyinward flow of transpiration fluid, as well as longitudinally along thecombustor, to achieve good mixing between the transpiration fluid streamand the combustion product while promoting an even axial flow of alongthe length of the combustion chamber. A third function of thetranspiration member can be to achieve a velocity of diluent fluidradially inward so as to provide a buffer for or otherwise interceptsolid and/or liquid particles of ash or other contaminants within thecombustion products from impacting the surface of the transpirationlayer and causing blockage, erosion, corrosion, or other damage. Such afactor may only be of importance, for example, when combusting a fuel,such as coal, having a residual inert non-combustible residue. The innerwall of the combustor pressure vessel surrounding the transpirationmember may also be insulated to isolate the high temperaturetranspiration fluid stream within the combustor.

In certain embodiments, a mixing arrangement (not illustrated) may beprovided to combine the materials to be introduced into the combustionapparatus 300 prior to such introduction. Specifically, any combinationof two or all three of the fuel, O₂, and circulating fluid (e.g., CO₂circulating fluid) may be combined in the optional mixing arrangementprior to introduction into the combustion apparatus 300.

The fuel 15 introduced to the combustion apparatus 300 (as the slurrystream 255) along with the Oz 120 and a recycled circulating fluid 503is combusted to provide a combustion product stream 320. In specificembodiments, the combustion apparatus 300 is a transpiration cooledcombustor, such as described above. Combustion temperature can varydepending upon the specific process parameters—e.g., the type of fuelused, the molar ratio of circulating fluid to carbon in the fuel asintroduced into the combustor, and/or the molar ratio of CO₂ to O₂introduced into the combustor. In specific embodiments, the combustiontemperature is a temperature as described above in relation to thedescription of the transpiration cooled combustor. In particularlypreferred embodiments, combustion temperatures in excess of about 1,000°C., as described herein, may be advantageous.

It also can be useful to control combustion temperature such that thecombustion product stream leaving the combustor has a desiredtemperature. For example, it can be useful for the combustion productstream exiting the combustor to have a temperature of at least about700° C., at least about 900° C., at least about 1,200° C., or at leastabout 1,600° C. In some embodiments, the combustion product stream mayhave a temperature of about 700° C. to about 1,600° C. or about 1,000°C. to about 1,500° C.

Specifically, the pressure of the combustion product stream 320 can berelated to the pressure of the circulating fluid that is introduced intothe combustion apparatus 300. In specific embodiments the pressure ofthe combustion product stream 320 can be at least about 90% of thepressure of the circulating fluid introduced into the combustionapparatus 300.

The chemical makeup of the combustion product stream 320 exiting thecombustion apparatus 300 can vary depending upon the type of fuel used.Importantly, the combustion product stream will comprise the majorcomponent of the circulating fluid (e.g., CO₂) that will be recycled andreintroduced into the combustion apparatus 300 or further cycles. Infurther embodiments, the combustion product stream 320 may comprise oneor more of water vapor, SO₂, SO₃, HCl, NO, NO₂, Hg, excess O₂, N₂, Ar,incombustibles and/or other particulate matter, and possibly othercontaminants that may be present in the fuel that is combusted. Thesematerials present in the combustion product stream may persist in theCO₂ circulating fluid stream unless removed, such as by processesdescribed herein.

Advantageously, according to the present disclosure, the combustionproduct stream 320 can be directed to a turbine 400 without thenecessity of first filtering out any particulate material in thecombustion product stream 320. In the turbine 400, the combustionproduct stream 320 is expanded to generate power (e.g., via a generator400 a to produce electricity). The turbine 400 can have an inlet forreceiving the combustion product stream 320 and an outlet for release ofa turbine discharge stream 410. Although a single turbine 400 is shownin FIG. 1, it is understood that more than one turbine may be used, themultiple turbines being connected in series or optionally separated byone or more further components, such as a further combustion component,a compressing component, a separator component, or the like.

The turbine 400 specifically can be a turbine having a blade designand/or overall design as otherwise described herein. Further, theturbine may incorporate transpiration cooling or other coolingtechnology, as described herein. In particular, the turbine design canbe one with such low blade velocity and ash particle impingementvelocity such as to enable the turbine to endure impingement withoutsignificant erosion. Transpiration cooling of the turbine further canprotect against particle erosion by creating a continuous flow barrierlayer of the transpiration fluid between the blade surface and theparticulate material passing through the turbine.

Returning to FIG. 1, the exemplary system and cycle further comprises afilter 5 downstream from the turbine 400. The turbine discharge stream410 can be passed through the filter 5 to remove the particulatematerials therefrom. The placement of the filter 5 downstream of theturbine 400, instead of upstream of the turbine, is an advantageouscharacteristic of the disclosure since the combustion product stream 320can be expanded across the turbine at the higher temperature andpressure when immediately exiting the combustor apparatus 300 and thuspower production may be maximized. The lower pressure and cooler turbinedischarge stream 410 can then be filtered in the filter 5 to remove theparticulate materials therefrom as particulate stream 7. The filteredturbine discharge stream 420 thus is provided substantially free fromparticulate material for further processing in the combustion cycle.

In specific embodiments, the filter 5 preferably can comprise aconfiguration that is effective for removing substantially all of theparticulate material present in the combustion product stream 320. Thefilter 5 may comprise a cyclone filter and/or a candle filter in someembodiments, and filtration may occur from about 300° C. to about 775°C. in some embodiments. In particular embodiments, removal ofsubstantially all of the particulates can encompass removal of at least95%, at least 96%, at least 97%, at least 98%, at least 99%, at least99.5%, or at least 99.8% by volume of the particulates present in thecombustion product stream. Such particulate removal efficiency of thefilter can be related to particle size. For example, the notedpercentage of particles removed can relate to the ability of the filterto retain particles having a diameter of at least about 0.1 μm, at leastabout 0.5 μm, at least about 1 μm, at least about 5 μm, at least about10 μm, at least about 25 μm, at least about 50 μm, at least about 100μm, or at least about 500 μm. In one embodiment the particles producedby combustion may be in the range from about 0.1 μm to about 100 μm, andthe filter may be configured to remove substantially all particles aboveabout 1 μm, above about 5 μm, above about 10 μm, above about 15 μm, orabove about 20 μm and reduce the total particulate levels to less thanabout 10 mg/m³, less than about 5 mg/m³, less than about 1 mg/m³, orless than about 0.5 mg/m³.

In particular embodiments (i.e., wherein CO₂ is used as a circulatingfluid), the filtered turbine discharge stream 420 can be passed througha heat exchanger unit 500 (which may be a series of heat exchangers) toform an unprocessed recycle stream 501. This unprocessed recycle stream501 can be passed through a cold water heat exchanger 520 to form stream521, which is passed to a separator 540 for removal of secondarycomponents (e.g., H₂O, SO₂, SO₄, NO₂, NO₃, and Hg) as a stream 542. Inspecific embodiments, the separator 540 can comprise a reactor thatprovides a contactor with sufficient residence times such that theimpurities can react with water to form materials (e.g., acids) that areeasily removed. A purified circulating fluid stream 541 from theseparator 540 can be passed through a compressor 550 to form stream 551,which can be further cooled with a cold water heat exchanger 560 toprovide a supercritical, high density CO₂ circulating fluid 561. Incertain embodiments, the purified CO₂ circulating fluid 541 can becompressed to a pressure of at least about 7.5 MPa or at least about 8MPa. A portion of stream 561 can be withdrawn as stream 562 for use asthe fluidizing medium in the mixer 250 to form the slurry stream 255.The supercritical, high density CO₂ circulating fluid stream 561otherwise is further pressurized in compressor 570 to form thepressurized, supercritical, high density CO₂ circulating fluid stream571. A portion of the CO₂ in stream 571 may be withdrawn as stream 572to a CO₂ pipeline or other means of sequestration. The remaining portionof the CO₂ can proceed as pressurized, supercritical, high density CO₂circulating fluid stream 573, which can be passed back through the heatexchanger 500 (or series of heat exchangers) to heat the stream. Inspecific embodiments, the CO₂ circulating fluid can be provided at adensity of at least about 200 kg/m³, at least about 300 kg/m³, at leastabout 500 kg/m³, at least about 750 kg/m³, or at least about 1,000 kg/m³after discharge from the cold water heat exchanger 560 (and prior topassage through the heat exchanger unit 500 for heating). In furtherembodiments, the density may be about 150 kg/m³ to about 1,100 kg/m³.Passage of the stream 551 through the cold water heat exchanger 560 cancool the CO₂ circulating fluid to a temperature of less than about 60°C., less than about 50° C., or less than about 30° C. The CO₂circulating fluid in stream 561 entering the second compressor 570 canbe provided at a pressure of at least about 12 MPa. In some embodiments,the stream can be pressurized to a pressure of about 15 MPa to about 50MPa. Any type of compressor capable of working under the notedtemperatures and capable of achieving the described pressures can beused, such as a high pressure multi-stage pump.

The heated, pressurized, supercritical, high density CO₂ circulatingfluid can exit the heat exchanger 500 as first stream 503 to be providedas the recycled circulating fluid. In some embodiments, the heated,pressurized, supercritical, high density CO₂ circulating fluid can exitthe heat exchanger 500 as a second recycled circulating fluid stream 504to be provided as a transpiration fluid for the turbine blades.Preferably, the second recycled circulating fluid stream 504 can becontrollable such that the total mass or volume of circulating fluid inthe stream can be increased or decreased as demand requires increasingor decreasing the protection provided by the transpiration fluid.Specifically, a system according to the disclosure can include flowcontrol means such that the second recycled circulating fluid stream 504can be completely stopped when desired.

Note that in some embodiments the recycled circulating fluid (e.g., CO₂)provided to the turbine 400 may bypass the heat exchanger 500 prior tobeing provided to the turbine. In this regard, the recycled CO₂ may becompressed by the compressor 570 and then a portion of circulating fluidstream 571 may bypass the heat exchanger 500 and enter the turbine 400.Thereby CO₂ (or other recycled circulating fluid) may be introduced intothe turbine 400 without being warmed by the heat exchanger 500.Accordingly, the CO₂ (or other recycled circulating fluid) may beintroduced into the turbine at a temperature that is less than thetemperature of fluid warmed by the heat exchanger. In this regard, theCO₂ (or other recycled circulating fluid) may be introduced into theturbine at a temperature of less than about 300° C., less than about200° C., less than about 100° C., less than about 55° C., or less thanabout 25° C. and thus, the CO₂ (or other recycled circulating fluid) maybe employed to cool the turbine 400. In order to compensate for addingrelatively cooler circulating fluid to the turbine 400, O₂ may travelthrough the heat exchanger 500 to warm the O₂ and then the O₂ may becombined with the recycled circulating fluid 503 directed to thecombustor 300 to compensate for the loss in efficiency that mayotherwise occur. In certain embodiments, circulating fluid leaving thecold end of the heat exchanger (or the final heat exchanger in theseries when two or more heat exchangers are used) can have a temperatureof less than about 200° C., less than about 100° C., less than about 75°C., or less than about 40° C.

In certain embodiments, it may thus be useful for the heat exchangerreceiving the turbine discharge stream to be formed from highperformance materials designed to withstand extreme conditions. Forexample, the heat exchanger may comprise an INCONEL® alloy or similarmaterial. Preferably, the heat exchanger comprises a material capable ofwithstanding a consistent working temperature of at least about 700° C.,at least about 900° C., or at least about 1,200° C. It also may beuseful for one or more of the heat exchangers to comprise a materialthat provides good chemical resistance to the type of secondarymaterials that may be present in the combustion product stream. INCONEL®alloys are available from Special Metals Corporation, and someembodiments can include austenitic nickel-chromium-based alloys.Suitable heat exchangers can include those available under the tradenameHEATRIC® (available from Meggitt USA, Houston, Tex.).

As noted above, in addition to water, the CO₂ circulating fluid maycontain other secondary components, such as fuel-derived,combustion-derived, and oxygen-derived impurities. These secondarycomponents of the CO₂ circulating fluid (often recognized as impuritiesor contaminants) can all be removed from the cooled CO₂ circulatingfluid using appropriate methods (e.g., methods defined in U.S. PatentApplication Publication No. 2008/0226515 and European Patent ApplicationNos. EP1952874 and EP1953486, which are incorporated herein by referencein their entirety). For example, SO₂ and SO₃ can be converted 100% tosulfuric acid, while >95% of the NO and NO₂ can be converted to nitricacid. Any excess O₂ present in the CO₂ circulating fluid can beseparated as an enriched stream for optional recycle to the combustor.Any inert gases present (e.g., N₂ and Ar) can be vented at low pressureto the atmosphere.

As described above, a power production cycle incorporating a turbinethat is configured according to the disclosure can operate at a highefficiency in part because the combustion product stream (e.g., arisingfrom combustion of a solid fuel, such as coal) can be inputted directlyinto the turbine without the need for first filtering out particulatematerial present in the combustion product stream. Particularly, theinventive turbine configurations eliminate or greatly reduce bladeerosion arising from impingement of the non-combusted material. Eventhough the disclosure provides such valuable protection of the turbinematerials, there still may be occasion for turbine impairment arisingfrom interaction of the turbine components with the particulatecomponents of the combustion product stream.

For example, liquid ash sticking and freezing (or solidifying) onto theturbine blades can cause slagging, loss of efficiency, and/or loss ofrotor balance. Accordingly, in certain embodiments, the presentdisclosure provides for incorporation of specific components into acombustion cycle for alleviating and/or at least partially removingbuildup or chemical deposits from turbine components, particularlyturbine blades. Although ash buildup is exemplified herein, it isunderstood that the cleaning provided by embodiments of the presentdisclosure would be expected to be effective in at least partiallyremoving or completely removing any type of deposit on the turbinecomponents arising from materials present in the combustion productstream, particularly particulate materials. Thus, various types of ash,ash derived material, and carbon may be removed by the cleaning providedherein.

Buildup of chemical deposits on turbine components, such as turbineblades, may be prevented by employing transpiration protectiontechniques. For example, as seen in FIG. 1, hot recycled working fluid(e.g., CO₂) can be withdrawn from the hot end of the heat exchanger 500as stream 504 and delivered to the turbine 400. For example, the hotrecycled working fluid can be delivered to the turbine rotor and thenthrough the turbine blades to provide transpiration protection of theturbine blades. In such embodiments, the turbine blades can beperforated as necessary so that a hot recycled working fluid exits theblades along substantially the entire surface of the blades, or at leastthe leading surface of the blades that is in the direct path of thecombustion product stream entering the turbine. In specific embodiments,the greatest flow of transpiration fluid out of the blades would be atthe leading edges of the blades.

The transpiration fluid may be provided at various temperatures. In someembodiments, the transpiration fluid for the turbine may be at atemperature that is within about 10%, within about 8%, within about 5%,or within about 2% of the temperature of the combustion product streamentering the turbine. In such embodiments, the temperature of thetranspiration fluid for the turbine may be characterized as beingsubstantially similar to the temperature of the combustion productstream entering the turbine. In other embodiments, the transpirationfluid directed to the turbine for transpiration protection may be 15% toabout 90% less than, about 15% to about 60% less than, about 15% toabout 50% less than, or about 20% to about 40% less than the temperatureof the combustion product stream entering the turbine. In suchembodiments, the temperature of the transpiration fluid for the turbinemay be characterized as being substantially less than the temperature ofthe combustion product stream entering the turbine.

In some embodiments, the use of the transpiration fluid with the turbineblades can perform multiple functions. For example, the transpirationfluid can be effective for protecting the turbine blades as it canessentially prevent particulate materials in the combustion productstream from actually contacting the blade surface. Rather, theprotective barrier formed by the transpiration fluid can deflect orotherwise redirect the particulate materials around the turbine blades.The hot recycled working fluid also can function to heat the blades,particularly the blade surfaces on the outlet side of the turbine. Thisadditional heating can prevent the blade surfaces, on the outlet sideand/or the inlet side, from cooling to a temperature wherein liquid ash(or other materials that are liquid at the temperature of the combustionproduct stream and have a freezing (or solidification) point that isless than the temperature of the combustion product stream but greaterthan ambient temperature) will solidify (i.e., the freezing temperatureof the material). This prevents the liquid particles that actuallycontact the surface of the turbine blade from freezing (or solidifying)and thus depositing on the blade surfaces.

Transpiration protection can eliminate particle freezing (orsolidifying) in some embodiments. In this regard, all ash may remainmolten above approximately 870° C.-980° C. in some embodiments. In otherembodiments, particle freezing can be reduced in relation to identicalcycles and systems that do not incorporate transpiration protection. Tothe extent particle freezing is reduced but not eliminated, periodiccleaning of the turbine components may be necessary. In specificembodiments, cleaning of turbine components, such as turbine blades, maybe effected through incorporation of cleaning components into acombustion cycle or system.

The cycle shown in FIG. 2 illustrates a system wherein turbine bladecleaning materials can be directed through the turbine to effectcleaning of the turbine blades. Beneficially, the cleaning materials maybe directed through the turbine in parallel with the combustion productstream. Thus, cleaning can be effected without interrupting the powerproduction combustion cycle. In some embodiments, it may be desirable toalter one or more of the cycle parameters discussed herein to facilitatethe cleaning process (e.g., to alter the temperature of the combustionproduct stream, to increase the ratio of recycle fluid to fuel, or thelike). In embodiments wherein the turbine blade is being transpirationprotected, it may be desirable to cease the transpiration fluid flow tofacilitate contact of the cleaning material with the turbine blades.However, combustion and power generation may continue during thecleaning process.

Referring to FIG. 2, a combustion cycle can proceed substantially asdescribed above in relation to FIG. 1. In the present embodiments,however, a third recycled circulating fluid stream 506 can exit the heatexchanger 500 and pass through a cleaning material junction 600 whereinthe cleaning material is combined with the third recycled circulatingfluid stream 506 to form the cleaning material stream 610. The cleaningmaterial junction 600 can comprise any structure, unit, or devicesuitable for combining the third recycled circulating fluid stream 506with the cleaning material wherein the cleaning material is provided ina continuous flow or is provided batchwise. Preferably, the cleaningmaterial junction is configured such that the cleaning material iscombined with and flows with the third recycled circulating fluid stream506. As also described above in relation to the second recycledcirculating fluid stream 504, the third recycled circulating fluidstream 506 can be controlled such that the flow rate can be zero or canbe any rate necessary to effectively transfer the cleaning material tothe turbine.

The cleaning material can be any material effective to contact thesurface of the turbine blades and physically or chemically remove soliddeposits therefrom. Preferably, the cleaning material comprises amaterial that is effective to remove the deposits with minimal to noerosion of the blade surfaces themselves. Solid cleaning materials mayinclude carbon particles, alumina particles, or other hard particlesconfigured to not melt at the flow temperatures. Erosion of ash but notthe blades may occur at the low impact velocities because the ash maydefine a lower fracture strength than the blade. Liquid cleaningmaterials may include potassium compounds such as potassium oxide,carbonate, or hydroxide. The potassium compounds may act as a flux tolower the melting point of the ash so it may melt off the blades.Gaseous cleaning materials may include oxygen which may oxidize depositssuch as carbon. Solid or liquid cleaning materials combined with thethird recycled circulating fluid stream 506 at the cleaning materialjunction 600 may define less than about 0.5%, less than about 0.1%, orless than about 0.01% of the total mass flow rate of the cleaningmaterial stream 610 and from about 0.001% to about 0.1%, from about 0.1%to about 1%, or from about 0.0001% to about 0.01% of the total mass flowrate of the cleaning material stream. Gaseous cleaning materialscombined with the third recycled circulating fluid stream 506 at thecleaning material junction 600 may define less than about 5%, less thanabout 2%, or less than about 1% of the total mass flow rate of thecleaning material stream 610 and from about 0.1% to about 2%, from about0.01% to about 1%, or from about 0.01% to about 5% of the total massflow rate of the cleaning material stream. In one embodiment thecleaning cycle may be initiated whenever the power output by thegenerator 400 a drops from about 2% to about 5%, from about 5% to about10%, or from about 1% to about 2%. For example, the cleaning operationmay be conducted from about once per week to about once every threeyears. The cleaning cycle may last from about five minutes to about onehour in some embodiments.

The cleaning material stream 610 may flow directly into the turbine 400.In such embodiments, the cleaning material stream may mix with thecombustion product stream 320 in a common inlet to the turbine 400, orthe cleaning material stream 610 and combustion product stream 320 mayhave individual inlets into the turbine such that the streams mix at apoint interior to the turbine 400. In the illustrated embodiment, thecleaning material stream 610 is first mixed with the combustion productstream 320 in a flow combiner switch 650. Thus, in a cleaning cycle, thecombined combustion product and cleaning material stream 326 exits theflow combiner switch 650 and enters the turbine 400.

In some embodiments, continuous cleaning may be used wherein someminimal flow of the third recycled circulating fluid stream 506 can bemaintained such that an amount of cleaning material is continuouslyintroduced into the turbine. The flow of the third recycled circulatingfluid stream 506 could be adjusted up or down periodically to increaseor reduce the cleaning capacity of the cycle. In other embodiments, thethird recycled circulating fluid stream 506 can be closed so that nocleaning material passes from the cleaning material junction 600 intothe flow combiner switch 650. In this mode of operation, the combustionproduct stream 320 may bypass the flow combiner switch 650 and passdirectly into the turbine, as illustrated in FIG. 1. Alternately, thecombustion product stream 320 may continue to flow through the combinerswitch 650 but, in the absence of an incoming cleaning material stream610, the stream exiting the combiner switch 650 would be essentially thecombustion product stream 320 and not the combined combustion productand cleaning material stream 326.

In embodiments wherein the cleaning cycle is active, the deposits orresidue removed from the turbine blades can be removed from the cyclevia the filter 5 in the manner described in relation to FIG. 1.Likewise, when solid cleaning materials are used, the solid cleaningmaterials can be removed from the cycle via the filter 5. In someembodiments, the filter 5 may be a multi-unit filter wherein a firstfilter media or unit is used in the normal course of the combustioncycle, and a second filter media or unit can be used during the cleaningcycle to collect the cleaning material and the removed blade depositswithout unnecessarily fouling the filter used in the normal combustioncycle. The inventive system could incorporate the appropriate devices tofacilitate such switching between filters.

Example Embodiments

The present disclosure will now be described with specific reference tothe following examples, which are not intended to be limiting of thedisclosure and are rather provided to show exemplary embodiments.

FIG. 3 illustrates an example embodiment of a combustor 1000 that may beemployed in accordance with the systems and methods disclosed herein.The combustor 1000 may define a combustion chamber 1002 into which fueland O₂ are directed through a fuel inlet 1004 and an O₂ inlet 1006.Accordingly, the fuel may be combusted to form a combustion productstream 1008. The combustor 1000 may comprise a casing comprising anouter casing 1010 and an inner casing 1012. The inner casing 1012 maycomprise a transpiration material such as a porous sintered material(e.g., a porous sintered metal material) that is configured to receive atranspiration fluid 1014 and transpire the fluid therethrough to definea transpiration layer 1016 configured to reduce the heat incident on thecasing. The transpiration fluid 1014 may be received in some embodimentsthrough an inlet 1026, although the transpiration fluid may be receivedfrom a turbine attached to the combustor in some embodiments, asdescribed below. Accordingly, the combustor 1000 may be configured towithstand the heat produced in the combustion chamber 1002 withoutemploying expensive heat resistant materials such as superalloys and/orthe combustor may operate at increased combustion temperatures.

As described above, the combustion product stream produced by acombustor may be employed to drive a turbine. In this regard, FIG. 4illustrates an example embodiment of a turbine 2000. In one embodimentthe turbine 2000 may include an inlet conduit 2002 configured to coupleto an outlet of a combustor (e.g., combustor 1000) and direct acombustion product stream (e.g., combustion product stream 1008) to aninlet of a casing 2004 of the turbine. The turbine 2000 may comprise arotor 2006 to which a plurality of blades 2008 are attached. The rotor2006 may comprise an annular flow diverter 2010 configured to divert thecombustion product stream around the rotor. Accordingly, the combustionproduct stream 1008 may be expanded while traveling through the turbine2000, thereby causing the blades 2008 to rotate the rotor 2006 and apower shaft 2011 (which may be integral with the rotor, or coupledthereto) before a turbine discharge stream 2012 is discharged throughone or more outlets 2014. Thus, the turbine 2000 may drive a generator,or other device.

As further illustrated in FIG. 4, the inlet conduit 2002 may comprise aninner casing 2016 and an outer casing 2018. Further, the casing 2004 ofthe turbine 2000 may comprise an inner casing 2020 and an outer casing2022. A transpiration fluid 2024 may be directed from an inlet 2026between the inner casings 2016, 2020 and the outer casings 2018, 2022 ofthe inlet conduit 2002 and the turbine 2000. The inner casings 2016,2020 may comprise a transpiration material such as a porous sinteredmaterial (e.g., a porous sintered metal material) that is configured toreceive the transpiration fluid 2024 and transpire the fluidtherethrough. Thereby a transpiration layer 2028 may be defined betweenthe combustion product stream 1008 and the inner surface of the inletconduit 2002 and a transpiration layer 2030 may be defined between theblades 2008 and an inner surface of the inner casing 2020 and the innercasings may be cooled or otherwise protected by the transpiration fluid2024. In some embodiments the transpiration fluid provided to theturbine may also be provided to the combustor for transpiration cooling.In this regard, for example, the inlet conduit may mate to the combustorsuch that the transpiration fluid is provided thereto in someembodiments. However, transpiration fluid provided to the combustor mayadditionally or alternatively be provided from a separate inlet 1026 insome embodiments.

Further, transpiration fluid 2024 may also be introduced into theturbine 2000 through a second inlet 2032, which may be defined in thepower shaft 2011 in some embodiments. Accordingly, the transpirationfluid 2024 may travel through the power shaft 2011 into the rotor 2006.The rotor 2006 and/or the blades 2008 may comprise a transpirationmaterial such as a porous sintered material (e.g., a porous sinteredmetal material) that is configured to receive the transpiration fluid2024 and transpire the fluid therethrough to outer surfaces thereof.Accordingly, the rotor 2006 and/or the blades 2008 may be cooled orotherwise protected from the combustion product stream 1008 andparticulates therein by the transpiration fluid 2024.

FIGS. 5 and 6 illustrate an alternate embodiment of a turbine 2000′. Asillustrated, a plurality of combustors 1000′ may be configured to drivethe turbine 2000′. In particular, the combustors 2000′ may be radiallydisposed with respect to a major axis defined by the rotor 2006′, asillustrated in FIG. 6. As shown in FIG. 5, the turbine 2000′ may besubstantially similar to the embodiment of the turbine 2000 illustratedin FIG. 4, except the combustors 1000′ may supply combustion productstreams 1008′ around the circumference of the rotor 2006′. Accordingly,an annular flow diverter may not be needed to divert the combustionproduct streams 1008′ around the rotor 2006′. Each of the combustors1000′ may be substantially similar to the combustor 1000 described aboveexcept for the placement of the combustors around the rotor 2006′.

FIG. 7 illustrates a lateral sectional view through an embodiment of aturbine blade 2008A that may be employed in the turbines disclosedherein. The turbine blade 2008A may comprise an outer layer 3002 and acore 3004. The core 3004 may define a relatively strong metal, or othermaterial configured as a reinforcement member. A strong metal, as usedherein, refers to a metal with a strength greater than about 10,000 PSI,greater than about 20,000 PSI or greater than about 30,000 PSI atappropriate elevated temperatures and that is chemically resistant atappropriate temperatures. Examples include stainless steel alloys andhigh nickel alloys such as Inconel, etc. Thus, the present disclosureallows lower cost alloys such as stainless steel (e.g., 316 stainlesssteel) or other alloys with lower nickel and cobalt contents to be usedinstead of the typical superalloys which have relatively very highnickel and cobalt contents, and are thus very expensive. In this regard,a polycrystalline 316 stainless steel can be as much as twenty timesless expensive per pound than a polycrystalline superalloy, andtwo-thousand times cheaper per pound than single crystal superalloyblades.

Further, the core 3004 may define one or more channels 3006. Thechannels 3006 may be configured to receive transpiration fluid anddirect the transpiration fluid into the outer layer 3002. The outerlayer 3002 may define a portion, or the entirety, of an exterior surface3008 of the blade 2008A in some embodiments. Further, the outer layer3002 may comprise a porous material such as a porous sintered metalmaterial. Accordingly, the channels 3006 in the core 3004 may beconfigured to receive transpiration fluid and direct the transpirationfluid into the outer layer 3002. Thus, the transpiration fluid may flowthrough the outer layer 3002 of the turbine blade 2008A and provide atranspiration layer around the exterior surface 3008 of the turbineblade which may protect the turbine blade from heat and/or impacts withparticulates. In this regard, it should be understood that a turbineblade and/or other components of the systems disclosed herein may betranspiration protected, meaning a transpiration fluid is directed to atleast a portion of a surface thereof, regardless of whether thetranspiration cools the component. For example, a component may betranspiration protected by a transpiration fluid that protects a surfaceof the component from impact with particulates or other matterregardless of the temperature of the transpiration fluid. Conversely, acomponent may additionally or alternatively be transpiration protectedby a transpiration fluid that cools the component or acts as a barrierthat reduces heating of the component.

As described above, transpiration fluid may additionally oralternatively be employed in other components associated with thesystems and assemblies described herein. In this regard, FIG. 8illustrates a sectional view through a portion of an inlet conduit 2002Aconfigured to deliver a combustion product stream from a combustor to aturbine. The inlet conduit 2002A may comprise an inner layer 4002 and anouter layer 4004. The outer layer 4004 may comprise a shell, which maycomprise a strong metal as described above, configured to providestrength to the inlet conduit 2002A. Further, the outer layer 4004 maydefine one or more channels 4006. The channels 4006 may be configured toreceive transpiration fluid and direct the transpiration fluid into theinner layer 4002. The inner layer 4002 may define a portion, or theentirety, of an inner surface 4008 of the inlet conduit 2002A in someembodiments. Further, the inner layer 4002 may comprise a porousmaterial such as a porous sintered metal material. Accordingly, thechannels 4006 in the outer layer 4004 may be configured to receivetranspiration fluid and direct the transpiration fluid into the innerlayer 4002. Thus, the transpiration fluid may flow through the innerlayer 4002 of the inlet conduit 2002A and provide a transpiration layerat the inner surface 4008 of the inlet conduit which may protect theinlet conduit from heat and/or impacts with particulates.

As illustrated in FIG. 9, in one embodiment of an inlet conduit 2002B,an insulation layer 4010 and a second outer layer 4012 may additionallybe provided. The insulation layer 4010 and the second outer layer 4012may surround the inner layer 4002 and the outer layer 4004 in someembodiments. The insulation layer 4010 may insulate the inlet conduit2002B so as to retain more heat therein, which may increase theefficiency of the system in which it is employed. Further, the secondouter layer 4012 may provide additional strength to the inlet conduit2002B. However, the various material layers and features described abovemay additionally or alternatively be employed in other components of thesystems and assemblies described herein, such as in a combustor.

FIG. 10 illustrates a longitudinal sectional view through a turbineblade 2008B in accordance with an alternate embodiment. The turbineblade 2008B may comprise one or more reinforcement members such as oneor more rods 5014. The rods 5014 may comprise a metal material, or othermaterial configured to provide strength to the turbine blade 2008B.

The turbine blade 2008B may further define one or more channels 5006.The channels 5006 may be configured to receive transpiration fluid anddirect the transpiration fluid into the material defining the turbineblade 2008B. In this regard, the turbine blade 2008B may comprise aporous material such as a porous sintered metal material. Accordingly,the channels 5006 in the turbine blade 2008B may be configured toreceive transpiration fluid and direct the transpiration fluid throughthe turbine blade to provide a transpiration layer at an outer surface5008 of the turbine blade which may protect the turbine blade from heatand/or impacts with particulates.

In some embodiments the turbine blade 2008B may be configured to definea flow of transpiration fluid at a leading edge 5016 of the turbineblade that is greater than a flow of the transpiration fluid at atrailing edge 5018 of the turbine blade. This may provide the leadingedge with greater protection, which may be desirable since the leadingedge may otherwise be more prone to impacts with particles than theremainder of the turbine blade. In this regard, one or more channels5006 in the turbine blade 2008B may define a transpiration fluid inletarea at the leading edge 5016 (see, e.g., channel 5006A) that is greaterthan a transpiration fluid inlet area of one or more channels at thetrailing edge 5018 (see, e.g., channel 5006B). Alternatively, a greaternumber of channels may be defined at the leading edge than at thetrailing edge.

FIGS. 11-13 illustrate an alternate embodiment of a turbine blade 2008C.As illustrated, the turbine blade 2008C may define an integral structurecomprising one or more internal ribs 6020. The internal ribs 6020 mayfunction as a reinforcement member configured to provide strength to theturbine blade 2008C. The internal ribs 6020 may be integrally formedwith an outer layer 6002 and/or a base member 6022 of the turbine blade2008C.

The turbine blade 2008C may include one or more channels 6006 that maybe separated by the internal ribs 6020. The channels 6006 may beconfigured to receive transpiration fluid (e.g., from a rotor to whichthe base member 6022 attaches) and direct the transpiration fluidthrough the outer layer 6002. In this regard, the turbine blade 2008Cmay comprise a porous material such as a porous sintered metal material.Accordingly, the channels 6006 in the turbine blade 2008C may beconfigured to receive transpiration fluid and direct the transpirationfluid through the outer layer 6002 of the turbine blade to provide atranspiration layer at an outer surface 6008 of the turbine blade whichmay protect the turbine blade from heat and/or impacts withparticulates. As further illustrated, the channels 6006 in the turbineblade 2008C may define a transpiration fluid inlet area at the leadingedge 6016 (see, e.g., channel 6006A) that is greater than atranspiration fluid inlet area of one or more channels at the trailingedge 6018 (see, e.g., channel 6006B). Accordingly, in some embodimentsthe turbine blade 2008C may be configured to define a flow oftranspiration fluid at a leading edge 6016 of the turbine blade that isgreater than a flow of the transpiration fluid at a trailing edge 6018of the turbine blade.

FIG. 14 illustrates a lateral cross-sectional view through an additionalembodiment of a turbine blade 2008D. As illustrated, the turbine blade20081) may comprise an outer layer 7002 that defines a wall thickness atthe trailing edge 7018 that is greater than a wall thickness at theleading edge 7016. In this regard, the turbine blade 2008D may comprisea porous material such as a porous sintered metal material. Accordingly,transpiration fluid may be directed through the turbine blade 2008D suchthat it travels through the outer layer 7002 to provide a transpirationlayer at an outer surface 7008 of the turbine blade which may protectthe turbine blade from heat and/or impacts with particulates. Since thewall thickness of the outer layer 7002 is greater at the trailing edge7018 than at the leading edge 7016, the turbine blade 2008D may define aflow of transpiration fluid at the leading edge that is greater than aflow of the transpiration fluid at the trailing edge.

Further, the turbine blades in accordance with the various embodimentsdisclosed herein may define a porosity that varies between the root andtip of a turbine blade (see, e.g., the root 6026 and tip 6028 of theturbine blade 2008C illustrated in FIG. 13). In this regard, in someembodiments the turbine blades disclosed herein may be configured todefine a flow of the transpiration fluid at the tip of the turbine bladethat is greater than a flow of the transpiration fluid at the root ofthe turbine blade. This may provide the turbine blades with additionalprotection which may be desirable since the tip of the turbine blademoves at a greater velocity than any other point on the turbine blade.

For example, FIG. 15A schematically illustrates a longitudinal sectionalview through a turbine blade 2008E. As illustrated, the turbine blade2008E defines a porosity that differs between the root 8026 and the tip8028. In particular, the turbine blade 2008E is more porous at the tip8028 than the root 8026 such that relatively more transpiration fluidmay flow out of the tip of the turbine blade than the root of theturbine blade. In this regard, the turbine blade 2008E may comprise aporous material such as a porous sintered metal material configured totranspire a transpiration fluid therethrough, as discussed above. Asillustrated, in some embodiments the porous material may define aplurality of layers 8030A-D, wherein the porosity of the layersincreases from root to tip. The layers 8030A-D may be defined bydifferent materials or by the same material which has been sintered tovarious extents, and hence the porosity thereof varies. In someembodiments the layers may be laminated together, although the layersmay be attached in various other manners.

In another embodiment, as illustrated in FIG. 15B, the turbine blade2008E′ defines a porosity that differs between the root 8026′ and thetip 8028′, as described above with respect to FIG. 15B. However, asillustrated, in some embodiments the porous material may define aporosity gradient, wherein, for example, the porosity of the materialincreases from the 8026′ to the tip 8028′. In this regard, the porosityof the material may change at various locations without there beingdistinct layers defining different porosities in some embodiments.

Various other configurations for the turbine blades may be employed. Forexample, in some embodiments the turbine blades may be configured todefine a flow of transpiration fluid at the leading edge that issubstantially equal to, or less than, the flow of transpiration fluid atthe trailing edge of the turbine blades. Further, in some embodimentsthe turbine blades may be configured to define a flow of transpirationfluid at the tip that is substantially equal to, or less than, the flowof transpiration fluid at the root of the turbine blade. Further,variations in porosity between the leading edge and trailing edge mayalso be used to control the flow of transpiration fluid out of theblades in a similar manner as described with respect to controllingtranspiration flow between the root and tip.

Thus, for example, the porosity of the material defining the turbineblade (or other component) may increase between the root and tip,decrease between the root and tip, be relatively higher or lower in thecenter relative to outer portions of the blade, increase or decreasefrom the leading edge to the trailing edge, etc. The porosity gradientor porosity layers may increase or decrease from about 10% porosity toabout 90% porosity, about 25% porosity to about 75% porosity, or about1% porosity to about 25% porosity.

Accordingly, transpiration fluid may be configured to cool and/orotherwise protect various components of the systems and assembliesdisclosed herein. In this regard, FIG. 16 illustrates a calculatedtrajectory 900 for a 100 μm ash particle 902 relative to an outersurface 904 of a turbine blade 906. The ash particle trajectory 900 ismodeled based on the ash particle 902 initially traveling at 75 m/stoward the turbine blade 906 with a flow of CO₂ transpiration fluid 908transpiring from the outer surface 904 of the turbine blade at 2 m/s.Circulating fluid in the turbine may be at 300 Bar (30 MPa) and 700° C.As illustrated, the transpiration fluid 908 prevents the ash particle902 from coming into contact with the turbine blade 906. In particular,the ash particle 902 is calculated to come about 0.2 mm from the outersurface 904 of the turbine blade. Accordingly, erosion of the turbineblade 906 may be avoided.

Similarly, FIG. 17 illustrates one example according to the presentdisclosure of a calculated particle trajectory 1000 for a 50 μm ashparticle 1002 relative to an inner surface 1004 of a combustor 1006. Theash particle trajectory 1000 is modeled based on the ash particle 1002initially traveling at a velocity of 50 m/sec perpendicular to the innersurface 1004 of the combustor 1006 with an axial flow velocity of thecombustion gas of about three meters per second, a combustion gascomposition of over about 90% CO₂, a combustion gas temperature of about1,500° C., a pressure of about 300 Bar (30 MPa), and a radialtranspiration flow rate of the transpiration fluid 1008 of about onemeter per second in the radial direction, (e.g., perpendicular to theaxial combustion gas flow). As illustrated, the transpiration fluid 1008prevents the ash particle 1002 from coming into contact with the innersurface 1004 of the combustor 1006. The ash particle 1002 is calculatedto come only about 0.2 mm from the inner surface 1004 of the combustor1006. Accordingly, erosion of the inner surface 1004 of the combustor1006 may be avoided.

Table 1 below provides various parameters for operation of aconventional power plant natural gas turbine design. A cross-section ofsuch typical turbine 1100 is shown in FIG. 18. As a comparative, Table 2below provides the same parameters for operation of a high pressure, lowvelocity turbine according to the present disclosure. A cross-section ofan exemplary turbine 1200 according to the disclosure is shown in FIG.19. As may be seen by comparing the conventional turbine 1100 to theturbine 1200 of the present disclosure, the turbine of the presentdisclosure may define a relatively smaller diameter due to the turbineof the present disclosure employing relatively shorter turbine blades2008F as compared to the turbine blades 1108 of the conventional turbinein some embodiments. In this regard, as shown in the following tables,the turbine blades 2008F of the turbine 1200 of the present disclosuremay define a relatively smaller average inner radius (i.e., from thecenter of the rotor 2006F to the root of the turbine blade), averageouter radius (i.e., from the center of the rotor to the tip of theturbine blade), and average radius (average of the inner and outerradii) as compared to the turbine blades 1108 of the conventionalturbine 1100 in some embodiments. Also, the turbine 1200 of the presentdisclosure may define a relatively greater length to diameter ratio ascompared to the conventional turbine 1100. Further, the turbine 1200 ofthe present disclosure may include a relatively larger number of turbineblades 2008F than the conventional turbine 1100. Additionally, thediameter of the rotor 2006F of the turbine 1200 of the presentdisclosure may be less than the diameter of the rotor 1106 of theconventional turbine 1100.

TABLE 1 Conventional Design Parameter Value Electrical Generator PowerRequirement 2.5 × 10⁸ W Turbine Inlet Pressure 15 bars (1.5 MPa) TurbineOutlet Pressure 1 bar (0.1 MPa) Combustion Product Flow Temperature1,623 K (1,350° C.) Flow Density 0.75 kg/m³ Flow Velocity 700 mph (310m/s) Turbine Length 10 m Turbine Diameter 4 m Number of blades 200

TABLE 2 Inventive Design Parameter Value Electrical Generator PowerRequirement 2.5 × 10⁸ W Turbine Inlet Pressure 300 bars (30 MPa) TurbineOutlet Pressure 30 bar (3 MPa) Combustion Product Flow Temperature 1,400K (1,127° C.) Flow Density 70 kg/m³ Flow Velocity 100 mph (44 m/s)Turbine Length 5 m Turbine Diameter 1.5 m Number of blades 1,000

Many modifications and other embodiments of the disclosure set forthherein will come to mind to one skilled in the art to which thedisclosure pertains having the benefit of the teachings presented in theforegoing descriptions. Therefore, it is to be understood that thedisclosure is not to be limited to the specific embodiments disclosedand that modifications and other embodiments are intended to be includedwithin the scope of the appended claims. Although specific terms areemployed herein, they are used in a generic and descriptive sense onlyand not for purposes of limitation.

1-62. (canceled)
 63. A turbine assembly, comprising: a casing defining:an inlet configured to receive a combustion product stream, and anoutlet; a rotor positioned in the casing; and a plurality of bladesextending from the rotor, wherein a ratio of a length of the turbineassembly to an average diameter of the blades is greater than about 3.5.64. The turbine assembly of claim 63, wherein the turbine blades have ablade height less than about 0.275 m.
 65. The turbine assembly of claim63, wherein the turbine assembly comprises less than about 2,000 of theblades.
 66. The turbine assembly of claim 63, wherein the blades aretranspiration protected.
 67. The turbine assembly of claim 66, whereinthe blades comprise a porous sintered material configured to direct atranspiration fluid to an exterior surface of the blades.
 68. Theturbine assembly of claim 67, wherein the porous sintered material isconfigured to define a flow of the transpiration fluid at a leading edgethat is greater than a flow of the transpiration fluid at a trailingedge.
 69. The turbine assembly of claim 68, wherein each of the bladesdefines a transpiration fluid inlet area at the leading edge that isgreater than a transpiration fluid inlet area at the trailing edge. 70.The turbine assembly of claim 68 wherein each of the blades defines awall thickness that is greater at the trailing edge than at the leadingedge.
 71. The turbine assembly of claim 68, wherein each of the bladesextends from a root at the rotor to a tip, and wherein the poroussintered material defines a porosity that varies between the root andthe tip.
 72. The turbine assembly of claim 71, wherein the porosity ofthe porous sintered material is configured to define a flow of thetranspiration fluid at the tip that is greater than a flow of thetranspiration fluid at the root.
 73. The turbine assembly of claim 71,wherein the porosity of the porous sintered material is configured todefine a flow of the transpiration fluid at the tip that issubstantially equal to a flow of the transpiration fluid at the root.74. The turbine assembly of claim 71, wherein the porous sinteredmaterial defines a plurality of layers, wherein the porosity of thelayers increases from the root to the tip.
 75. The turbine assembly ofclaim 67, wherein the inlet of the casing is configured to coupledirectly to an outlet of a combustor assembly.
 76. The turbine assemblyof claim 75, wherein the inlet of the casing is configured to receivethe combustion product stream from a plurality of combustors radiallydisposed with respect to a major axis defined by the rotor.
 77. Theturbine assembly of claim 67, wherein the porous sintered materialdefines the entirety of the exterior surface of the blades.
 78. Theturbine assembly of claim 67, wherein the casing comprises the poroussintered material and the porous sintered material is configured todirect the transpiration fluid to an interior surface of the casing. 79.The turbine assembly of claim 67, wherein the rotor comprises the poroussintered material and the porous sintered material is configured todirect the transpiration fluid to an exterior surface of the rotor. 80.The turbine assembly of claim 67, wherein the rotor comprises an annularflow diverter configured to divert the combustion product stream aroundthe rotor.
 81. The turbine assembly of claim 67, further comprising aninlet conduit coupled to the inlet of the casing and configured tocouple to an outlet of a combustor assembly and receive the combustionproduct stream therefrom, wherein the inlet conduit comprises the poroussintered material and the porous sintered material is configured todirect the transpiration fluid to an interior surface of the inletconduit.
 82. The turbine assembly of claim 67, wherein the bladesrespectively further comprise at least one reinforcement member.